Research On Mechanical Behavior Of Steel-concrete Composite Frame With CFST Columns Exposure To Non-uniform Fires

At present,concrete filled steel tube(CFST)structure with its many advantages has got application in more and more high and ultra-high buildings,fire disaster is one of the common disasters which will pose a threat to public safety and social development in our daily life,study the effect of fire on the structure performance is of great significance.However,Fire happens in the local area of the structures,it is necessary to further study on the mechanical behavior of steel-concrete composite frame after exposure to non-uniform fires and analyze the deformation and failure mechanism of the frame with non-uniform fire.For the research by non-uniform fire in steel concrete composite frame mechanics performance,the main research works are as follows:(1)On the basis of the reasonable selection of thermal and mechanical materials,using ABAQUS to build concrete filled steel tube column models under one side and three side fire loading including loading at ambient,heating,cooling and post-fire,and analyze its the change rules of deformation and bearing capacity after the fire.It is to lay a foundation for the further research of non-uniform fire in steel concrete composite frame mechanics performance.(2)By building the existing test finite model of concrete-filled steel tube column frame of the reinforced concrete beam,the rationality of the modeling method is validated.With MIDAS software to design the steel concrete composite frame in this paper,and select a part of the frame for analyses.What's more,this article has analyzed the fire performance and mechanical performance of overall stage fire on the typical fire condition when the fire occurred in the middle part of the composite plane frame.(3)Using ABAQUS software build a 9-story 3 bay finite element model of steel concrete composite plane frame,analyses are carried on different typical fire conditions of deformation and failure mechanislm.The part which is exposure to fire is used entity unit(C3D8)modeling,the other part which is not affected by the fire adopts beam element(B31)modeling.The interface definition contact is with coupling methods.In a sequential thermal and mechanical coupling way,the temperature calculation results are used in the mechanical model analysis.